It is proposed to exploit in vitro techniques to further our information on two separate biosynthetic pathways which have been found to occur in marine shrimp: (1) the biosynthesis of radioactive homarine (N-methyl picolinic acid) from glycine; (2) the biosynthesis of quinolinic acid and N-methyl quinolinate from acetate. Quantitative methods which have been developed for the isolation, identification and preparation of esterified pyridine mono- and dicarboxylic acids will permit a study of potential biosyntheses of such compounds by marine crustacea. C14-labeled homarine will be chemically synthesized and injected into shrimp in order to determine the biological half-life and metabolic fate of homarine.